Which health care bill are Republicans voting on next week? No one knows yet.

WASHINGTON — The Senate is taking a key vote that could reshape the American health care system on Tuesday — but no one is exactly sure what they’ll be voting on.

Senate Majority Leader Mitch McConnell announced on Tuesday that his caucus had failed to coalesce around an Obamacare replacement plan and would instead move to a vote next week to begin debate on a “clean” repeal bill, to take effect in two years — allowing one more election cycle to pass before the need to come up with a replacement. The Congressional Budget Office estimated Wednesday that 32 million fewer Americans would have insurance under the repeal-only plan over 10 years.

At least four Senate Republicans have balked, saying they will not vote to proceed on a bill that repeals Obamacare without some kind of replacement. That means McConnell’s repeal-only motion would fail.

McConnell has vowed to hold the vote anyway, potentially putting some of his more vulnerable members in danger when they have to defend their vote for or against repealing Obamacare in 2018 and 2020 elections — from the left or the right. The conservative lobby Club for Growth has already rolled out a website featuring “Obamacare Repeal Traitors” — Republican members of the Senate who have said they would vote no on the motion. And any senator who votes yes may face Democratic attack ads saying they voted to kick 32 million Americans off insurance.

Facing this political pressure, the once-dead replacement bill appears to have come back to life, as McConnell dangled it in front of his caucus as a potential way out of the repeal-only trap.

“I think we have two options here,” McConnell told reporters after leaving a White House lunch on Wednesday with most of his caucus and President Trump. “I think we all agree it’s better to both repeal and replace. But we could have a vote on either.”

In the meeting, Trump told senators he wanted them to stay in Washington until they agreed on a path forward on health care, and pressured them to vote for the motion to start debate next week on a bill. The president has flip-flopped repeatedly on whether he wants a clean repeal or a repeal and replace.

“Any senator who votes against starting debate is really telling America you’re fine with Obamacare,” Trump said, reading the words from a piece of paper to the senators at one point.

Now, some Republican senators are saying they want to give their replacement bill one more try. The bill stalled after Mike Lee, R-Utah, Jerry Moran, R-Kan., Susan Collins, R-Maine, Rob Portman, R-Ohio and Rand Paul, R-Ky., all came out against it for different reasons. At least four other senators were likely no votes as well, but didn’t announce their opposition. Now, many of these holdouts are meeting with Senate leadership Wednesday night to try to hash out a deal, Axios reported.

“We’re trying to get to replace, and I think we have a shot, we’re going to take one more shot at it,” Sen. John Thune, R-S.D., told NBC News.

Sen. Mike Rounds, R-S.D., also said Wednesday he’s “not ready to give up on the bill” and believes it’s possible to get 50 members of the caucus to agree on it.

The pressure McConnell is putting on his members is causing some resentment among those who want to start over and move the health care debate to an open committee process.

Sen. Ron Johnson, R-Wis., told Yahoo News he wants to spearhead a rigorous analysis of how to fix the current system in committee starting next week.

Asked if it made sense to force a vote on clean repeal before giving Senate Republicans a chance to find a new plan, Johnson responded, “Talk to leadership in terms of what their thinking is there.”

“I would approach this process differently,” he added.

Johnson said if he was “forced” to vote on a motion to proceed on clean repeal next week, he would vote yes.

“When you’re trying to solve a complex problem you need to start with a rigorous process to gather as many facts as possible before you start setting achievable goals and certainly before you start designing the legislation,” Johnson said.

Other Republican senators, however, are embracing the repeal-only route, and say they aren’t thinking of the political consequences.

“That’s not the way I’m looking at it,” Sen. Pat Toomey, R-Pa. said. “We’ve made a commitment for seven years and God knows how many times. Let’s have the vote. Let’s go on record.”

Whether they’ll be voting on a revived version of the repeal-and-replace plan or the clean-repeal bill they’ve been campaigning on for years remains to be seen.